Thanks for both replies, which both make sense.  The weather has been awful, so the sparrowhawk could well have been hungry.  I found an early evening/daytime barn owl a few years ago, breeding where we didn’t suspect it, after a previous night of heavy rain.  I can’t be 100% that it was hunting bats, but chasing something in the near-dark is very likely.  If anyone else sees something similar, I would be interested to hear.

Mandarins are almost unavoidable at Orchardleigh Lake at the moment, with perhaps 5 or 6 pairs nesting around the two lakes.

Dan,
    I have seen a Hobby take a bat but never a Sparrowhawk.  In “The Sparrowhawk” by Ian Newton (Poyser, 1986), it records that studies over Europe as a whole suggest that mammals form less than 3% of food items (except during vole plagues in N.Europe), with at least 17 species reported, including “various bats”.  It seems you were definitely in the right place at the right time.

It’s entirely possible.  The sparrowhawk may have been prevented from hunting during the day by the miserable weather and was simply being opportunistic.  Bats are sometimes the prey of diurnal birds of prey (and owls) and it’s postulated that one reason for bats being nocturnal is to reduce the risk of predation.  This theory is given weight by the following:  The only species of bat that regularly flies by day is the Azores Noctule and it is thought to have adopted this behaviour because there are no aerial predators on the islands: https://en.wikipedia.org/wiki/Azores_noctule.

On Sunday in the dusk at Orchardleigh, at 8.10pm (15 mins after sunset) on a grey dull evening, a male sparrowhawk came into the tree I was sitting below.  It then belted off across the pond, into another tree, then fast jinking around as if chasing something.  No small birds around as it was too late, so I thought bat hunting.  I looked on youtube, and there is one video of one eating a small bat on a post, heralded as the first evidence of this, but no mention of actual hunting.  Anyone ever seen this happening?

Also, at 8.25pm, a pair mandarin ducks spent at least 10 minutes mating less than 20ft from me. 

A good evening!